Work machines such as, for example, wheel loaders, track type tractors, and other types of heavy machinery are used for a variety of tasks. These work machines include a power source, which may be, for example, an engine such as a diesel engine, a gasoline engine, or a natural gas engine, that provides the power required to complete these tasks. To efficiently perform these tasks, the power source may be coupled to a generator to produce an electrical power output supplied to one or more electric motors. The motors may be connected to ground engaging devices to propel the work machine.
Typically, the generator is commanded to produce power when a voltage level of an energy storage device disposed between the generator and the motor drops below a predetermined level and to stop producing power when the voltage level of the energy storage device exceeds a predetermined level. For example, U.S. Pat. No. 6,333,620 (the '620 patent) issued to Schmitz et al. on Dec. 25, 2001 describes a series type hybrid vehicle having a power source, a generator, a battery array, at least one electric motor, and a controller. The controller is configured to maintain a state of charge of the battery array within a control limit. The controller compares a state of charge of the battery array to an upper control limit and decreases generator output if the state of charge is equal to or greater than the associated upper control limit. The controller is further configured to increase generator output if the state of charge is less than the upper control limit.
Although the controller of the '620 patent may maintain a sufficiently constant state of charge of the battery array, the controller may require complex and expensive components necessary to respond quickly to power demand fluctuations. In addition, the battery array may provide insufficient acceleration and regenerative braking capacity.
The present disclosure is directed to overcoming one or more of the problems set forth above.